Field
Exemplary embodiments relate to lithographic exposure technology, and more particularly, to an exposure mask used in the manufacture of display substrates.
Discussion
A substrate, such as a display substrate, typically includes a base substrate, a gate layer disposed on the base substrate, a source/drain layer disposed on a portion of the gate layer, and an organic insulating layer disposed on the gate layer and the source/drain layer.
Typically, a gate driving part configured to output a gate signal to a gate line in the display substrate is disposed in a peripheral area of the display substrate. As such, an amorphous silicon gate (ASG) configured to output the gate signal to the gate line may be disposed on the display substrate.
The gate driving part typically includes a plurality of stages. Each of the stages usually includes a plurality of thin-film transistors. A gate electrode and a source electrode in the thin-film transistors may be electrically connected with each other, or the gate electrode and a drain electrode may be electrically connected with each other. As such, the gate layer and the source/drain layer may be connected with each other.
To effectuate the above-noted electrical connection(s), a first contact hole (or via) exposing the source/drain layer and a second contact hole exposing the gate layer may be formed through the organic insulating layer by patterning the organic insulating layer and depositing a conductive material to electrically connect the source/drain layer with the gate layer. Patterning may be achieved via one or more lithographic exposures.
A portion of the organic insulating layer disposed on the gate layer, however, may be thicker than a portion of the organic insulating layer disposed on the source/drain layer and the gate layer. Accordingly, if the patterning is done to form the first and second contact holes in the same process, the gate layer may not be exposed during an exposure of the organic insulating layer to expose the source/drain layer. As such, the gate layer may not be sufficiently exposed, and thereby, defects in the substrate may result. To this end, multiple exposure techniques may be utilized, but this can increase production costs, as well as introduce the possibility of alignment inconsistencies between multiple exposure masks. Therefore, there is a need for an approach that provides efficient, cost effective fabrication techniques to sufficiently pattern the organic insulating layer to expose underlying layers disposed at different depths and that also avoids defects.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.